Subwavelength Metal Hole Arrays Research Articles

A theoretical study of optically enhanced transmission characteristics of subwavelength metal Y-shaped arrays and its application on refractive index sensor

In this paper, the electric field distributions and transmission characteristics of subwavelength Y-shaped metal hole arrays are studied by using the finite element method (FEM). The results show that the Y-shaped metal hole arrays can achieve light-enhanced transmission in the subwavelength region, and the electric field distributions around the corners are stronger. When the energy of surface plasmon polaritons (SPPs) and local surface plasmon (LSP) are similar, it is more favorable for the transmission of metal nanohole structure. In addition, the influence of the inclined angle, thickness, width, and period on the transmission of this structure is also discussed. The effect of the inclined angle on the transmission characteristics is particularly obvious. As the angle increases, the transmittance increases from 0.558 to 0.628 at the wavelength of 0.67 μm, and the transmittance of 0.289 at the wavelength of 1.08 μm increases to 0.840 at 1.17 μm. Through the optimization of structural parameters, we achieve a theoretical value of the refractive index sensitivity (S) as high as 900 nm/RIU, and the corresponding sensing resolution is 2.22 × 10−4 RIU. These results would be helpful in designing the refractive index sensor of high-sensitivity and band-pass filters, and have guiding significance for biological sensor applications.

Survival of the orbital angular momentum of light through an extraordinary optical transmission process in the paraxial approximation.

We report on the extraordinary optical transmission (EOT) of an orbital angular momentum (OAM) state of light in the paraxial approximation. The OAM state transmits through a subwavelength metal hole array with a square structure, and then is analyzed by using a Mach-Zehnder interferometer. In the experiment, the transmitted light well conserves the OAM information while the transmission efficiency of the OAM mode is much greater than 1 (i.e., EOT works). Further study shows that the OAM mode has no significant influence on the transmission spectrum of the EOT paraxial process under our experimental configuration. Our work can be useful for future plasmon-based OAM devices.

周期性亚波长金属孔阵列的单元结构对称性对其增强光透射特性的影响

周期性亚波长金属孔阵列的单元结构对称性对其增强光透射特性的影响

30am2-PN-60 光波長計測のための金属ホールアレイ構造を有するナノメカニカル振動子の作製

A nanomechanical resonator for wavelength detection was proposed. The sub-wavelengh metallic hole array were applied for the nanomechanical resonator in order to generate surface plasmon. Surface plasmon was used for the device son that light absorption rate had the wavelength dependence. Surface plasmon generate on both side of sub-wavelength metallic hole array. In this study, both sides of the sub-wavelengh metallic hole array were covered with same dielectric materials in order to improve the light wavelength sensitivity. We examined the wavelength sensitivity of the device in the region from 1547 to 1563 nm. The wavelength sensitivity of the device which we proposed in this research was 9.13 pm.

Microscopic analysis of surface Bloch modes on periodically perforated metallic surfaces and their relation to extraordinary optical transmission

We build up a microscopic description of the surface Bloch mode (SBM) on metallic surfaces patterned with a periodic array of subwavelength holes. The SBM also is called a spoof surface plasmon when metals approach perfect electric conductors at terahertz or microwave frequencies. In the description, the SBM is found to be composed of surface waves on flat metallic surfaces, the surface plasmon polariton (SPP), and the quasicylindrical wave (QCW) launched by every individual hole in the array, which shines new light on the design of perforated metallic surfaces as plasmonic metamaterials. We also establish explicit relations between the macroscopic SBM picture and the microscopic surface-wave picture for explaining the extraordinary optical transmission (EOT) through subwavelength metallic hole arrays. Our analysis shows that the SBM is related tightly to the EOT through a complex pole of the in-plane wave vector at which the SBM and the EOT possess similar field distributions expressed as superpositions of the SPPs and QCWs.

Extraordinary Transmission Based on Deep Perforated Sub-Wavelength Metallic Hole Arrays for Infrared Photodetector

In this paper, a new mode of deep perforated sub-wavelength metallic hole arrays in hexagonal lattice is presented. The transmission spectrum is obtained with Finite-difference time-domain (FDTD) and measured with Fourier infrared spectrometer. In the resonance peak scope, the Electric-field intensity is similar to 80 times larger than that of the incident wave at near field. The resonance of this structure can enhance the near-field intensity and improve the absorption efficiency of photodetector.

Suppressed Optical Transmission Through an Array of Ultrathin Interlayer Metal Slits

In contrast to the enhanced peak transmission in a subwavelength metal hole array structure (Ebbesen et al., Nature 391:667–669, 1998), here we theoretically investigate the spectral transmission through an array of identical metal slits with ultrathin interlayers and surprisingly find the depressed optical transmission for both infinite and finite array case. Notably, in the latter system, the narrowband dip transmission is evidently produced with the accompaniment of selective field enhancement and phase jumping across the structure. Analyses suggest that this phenomenon is intrinsically related to the penetrant coupling of intracavity surface plasmon polaritons together with the slit termination effect.

Optical bistability in nonlinear subwavelength metal hole array involving Kerr materials

We investigate an optical bistability phenomenon in a structure consisting of a silver film with a hole array filling with Kerr medium with single wavelength. We explore the mechanism of optical bistability in our structures and find that the excitation condition of surface plasmon at this moment is related with that at last moment. The contrast of optical bistability can reach to the maximum at the wavelength of the transmission peak. Our structure can realize the function of the beam splitter.

NAnalysis of subwavelength metal hole array structure for the enhancement of back-illuminated quantum dot infrared photodetectors

This paper is focused on analyzing the impact of a two-dimensional metal hole array structure integrated to the back-illuminated quantum dots-in-a-well (DWELL) infrared photodetectors. The metal hole array consisting of subwavelength-circular holes penetrating gold layer (2D-Au-CHA) provides the enhanced responsivity of DWELL infrared photodetector at certain wavelengths. The performance of 2D-Au-CHA is investigated by calculating the absorption of active layer in the DWELL structure using a finite integration technique. Simulation results show that the performance of the DWELL focal plane array (FPA) is improved by enhancing the coupling to active layer via local field engineering resulting from a surface plasmon polariton mode and a guided Fabry-Perot mode. Simulation method accomplished in this paper provides a generalized approach to optimize the design of any type of couplers integrated to infrared photodetectors. Experimental results demonstrate the enhanced signal-to-noise ratio by the 2D-Au-CHA integrated FPA as compared to the DWELL FPA. A comparison between the experiment and the simulation shows a good agreement.

Subwavelength B-shaped metallic hole array terahertz filter with InSb bar as thermally tunable structure

We propose a subwavelength B-shaped metallic hole array filter with an embedded thermally tunable InSb semiconductor bar in the terahertz regime. The resonance frequency of this filter can be actively tuned by controlling the temperature of InSb. The transmissions of the filter are calculated with the finite-difference time domain method at various temperatures. Narrowband THz wave with the full width at half maximum of 235 GHz can be selected in the frequency range from 0.74 to 2.02 THz at temperatures from 160 to 350 K.

Terahertz coherent control of surface plasmon polariton propagation in subwavelength metallic hole arrays

We demonstrate the terahertz coherent control of extraordinary transmission through subwavelength metallic hole arrays with double terahertz pulses. The interference of excitations of surface plasmon polaritons (SPPs) by two THz pulses sequence is employed to control the propagation of SPPs in the periodical structure. As a result, the THz wave transmission is controllable by adjusting the arriving time of the control THz pulse. Our results reveal that THz extraordinary transmission in subwavelength structure arises from the excitation of SPPs of the structures, which provides a universal ultrafast means to control the SPPs motion in various THz subwavelength structures.

Surface electromagnetic modes contribution to the anomalous terahertz transmission through double-layered metal hole array

Terahertz transmission spectra through both single-layered and double-layered sub-wavelength metal hole arrays were calculated using rigorous mode-matching method. The dispersion relations of the single-layered and double-layered metal hole arrays were obtained by FDTD method. There are three anomalous peaks in the spectrum of the double-layered metal hole array, which arise from the three surface electromagnetic modes appearing in the dispersion relation. By comparing the transmission spectra and the dispersion relations of the single-layered and double-layered metal hole arrays, it was found that the two surface electromagnetic modes at higher frequencies are introduced by the single-layered metal hole array, while the one at lower frequencies is introduced by the double-layered metal hole array. The validity of the analysis was qualitatively verified by the experimental results. This structure can be finely designed for potential applications, such as wideband filtering.

Propagation dynamics of femtosecond pulse through subwavelength metallic hole arrays

We have studied the frequency-dependent transmission time delay of femtosecond (fs) laser pulses through subwavelength hole arrays in aluminum films using the up-conversion technique. The pulse delays measured at different wavelengths mainly follow the far-field transmission profile of the surface-plasmon polariton (SPP) resonances. Temporal delays of 60 and 100 fs were found at the major SPP resonance in the single-layer and double-layer samples. A coupled-SPP transmission model is used to explain the temporal dynamics of the transmission process. Our experiment shows that the weak coupling between the SPP waves on different metal-dielectric interfaces leads to the large temporal delay of the transmitted pulses.

The mechanism of the polarization dependence of the optical transmission insubwavelength metal hole arrays

We investigate the mechanism of extraordinary optical transmission in subwavelengthmetal hole arrays. Experimental results for the arrays consisting of square or rectangularholes are well explained by the dependence of transmission strength on the polarizationdirection of the incident light. This polarization dependence occurs in each single hole. Fora hole array, there is in addition an interplay between the adjacent holes which iscaused by the transverse magnetic field of surface plasmon polaritons on themetal film surfaces. Based on the detailed study of a single-hole and two-holestructures, a simple method to calculate the total transmissivity of hole arrays isproposed.

Ultrafast optical control of terahertz surface plasmons in subwavelength hole arrays at room temperature

We demonstrate optical control of surface plasmon enhanced resonant terahertz transmission in two-dimensional subwavelength metallic hole arrays fabricated on gallium arsenide based substrates. Optically pumping the arrays creates a conductive layer in the substrate, reducing the terahertz transmission amplitude of both the resonant mode and the direct transmission. Under low optical fluence, the terahertz transmission is more greatly affected by resonance damping than by propagation loss in the substrate. An ErAs:GaAs nanoisland superlattice substrate is shown to allow ultrafast control with a switching recovery time of ∼10 ps.

Mid-infrared doping tunable transmission through subwavelength metal hole arrays on InSb

Doping-tunable mid-infrared extraordinary transmission is demonstrated from a periodic metal hole array patterned on n-InSb. The polarization-dependent transmission was measured at room temperature and 77 K. In addition, the extraordinary transmission was measured for incident angles from 0 degrees to 35 degrees in 5 degrees steps. A fundamental resonance shift of approximately 123 cm-1 (1.4 microm) is observed by varying the doping from 1 x 10(16) to 2 x 10(18) cm(-3). The calculated transmission resonances were in good agreement with the experimental results. This suggests that InSb semiconductor-based plasmonic structures may be suitable for a variety of tunable mid-infrared device applications.

Composite metamaterials with dual-band magnetic resonances in the terahertz frequency regime

Composite metamaterials (CMMs) combining a subwavelength metallic hole array (i.e. one-layer fishnet structure) and an array of split-ring resonators (SRRs) on the same board are fabricated with gold films on a silicon wafer. Transmission measurements of the CMMs in the terahertz range have been performed. Dual-band magnetic resonances, namely, an LC resonance at 4.40 THz and an additional magnetic resonance at 8.64 THz originating from the antiparallel current in wire pairs in the CMMs, are observed when the electrical field polarization of the incident light is parallel to the gap of the component SRR. The numerical simulations agree well with the experimental results and further clarify the nature of the dual-band magnetic resonances.

Mid-infrared transmission enhancement through sub-wavelength metal hole array using impedance-matching dielectric layer

The mid-infrared transmission through a 3.7 µm period, two-dimensional sub-wavelength Au metallic hole array integrated on a GaSb/InAs strained layer superlattice nBn photodetector is measured. The surface plasmon-polariton excitation on the Au film induces a peak transmission in the 200 K detector response at 4.2 µm. This transmission is enhanced threefold by the insertion of a SiNx layer between the Au film and the substrate for impedance matching analogous to antireflection coating.

Electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays

We describe the electronic control of extraordinary terahertz transmission through subwavelength metal hole arrays fabricated on doped semiconductor substrates. The hybrid metal-semiconductor forms a Schottky diode structure, where the active depletion region modifies the substrate conductivity in real-time by applying an external voltage bias. This enables effective control of the resonance enhanced terahertz transmission. Our proof of principle device achieves an intensity modulation depth of 52% by changing the voltage bias between 0 and 16 volts. Further optimization may result in improvement of device performance and practical applications. This approach can be also translated to the other optical frequency ranges.

Enhanced Gain by Double-Periodic Stacked Subwavelength Hole Array

Using a doubly periodicity structure the extraordinary transmission of subwavelength metallic hole arrays in the microwave range can be boosted. Stacking several of such plates a left-handed metamaterial can be obtained as it is shown by the computed dispersion diagrams as well as the amplitude and phase measurements. An effective refraction index along the propagation direction can be calculated, giving a negative magnitude between -1 and 0. This enhances the emission by a focused beam with narrow beamwidth. Several practical applications like novel antennas are envisaged.